A high-pressure pump has a plunger which reciprocates to pressurize fuel in a pressurizing chamber. When the plunger slides down, the fuel is suctioned into a pressurization chamber through a suction passage. When the plunger slides up, the metered quantity of fuel is pressurized to be discharged through a discharge passage. JP-2004-138062A shows such a high-pressure pump in which a cylinder engaged with a housing has a through-hole through which a plunger is slidably inserted. The pressurization chamber is defined between an inner wall of the housing and an outer wall of the plunger.
It has been required that a high-pressure fuel discharges large quantity of fuel in high pressure. A housing receiving high pressure force from a pressurization chamber should have enough thickness to endure the high pressure force. In the high-pressure pump shown in JP-2004-138062A, the housing is thick and heavy. Moreover, as the fuel pressure in the pressurization chamber becomes higher, higher sealing is required between the housing and the cylinder. If the cylinder is firmly engaged with the housing to enhance the sealing therebetween, it is likely that an outer wall surface of the cylinder may be damaged when inserted into the housing. This damage on the cylinder may deteriorate the sealing therebetween.